A Non-Uniform Frequency Dithering Technique to Attenuate Electromagnetic Interference (EMI) in a SiC MOSFET-based DC-DC Buck Converter

The major challenge with wide-bandgap (WBG) device-based power electronic converters is the electromagnetic interference (EMI) associated with them. This demands EMI filters, which are often bulky in size, causing lower power density. As a solution, the widely used frequency dithering techniques in literature to reduce EMI noise and filter size often do not consider the effect of Resolution Bandwidth (RBW), causing the violation of international standards. This paper proposes a non-uniform frequency dithering technique with 15 switching frequencies with 1 kHz frequency steps from 32−46 kHz having unequal persisting time or dithering duties for each of the selected switching frequencies. This paper also focuses on the sidebands produced due to frequency dithering, and the effective noise reduction is calculated with an RBW of 9 kHz, considering the noise floor, which has been largely neglected in the literature. The proposed technique achieves a significant noise reduction of 10dBµV over the conducted EMI zone as compared to single-frequency operation. The experimental validations are performed on a 1 kW SiC MOSFET-based DC-DC buck converter prototype.